Methemoglobinemia and local anaesthesia

I have an MD in the family who says that almost any “Caine” can cause serious problems with blood oxygenation and that they were taught in med school of a few instances of deaths due to OTC numbing agents like Orajel. Is this true?

Both benzocaine and lidocaine can produce a rare condition called methemoglobinemia, in which proteins binding oxigen in blood get oxidized and cannot transport oxigen.